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| Subject Categories: Proteins | Immunology |
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| The EMBO Journal
(2002) 21, 2655–2663, doi: 10.1093/emboj/21.11.2655 |
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| The oxidoreductase ERp57 efficiently reduces partially folded in preference to fully folded MHC class I molecules |
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| Antony N. Antoniou1, Stuart Ford1, Magnus Alphey1, Andrew Osborne1, Tim Elliott2 and Simon J. Powis1 |
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1 Division of Cell Biology and Immunology, School of Life Sciences, University of Dundee, Dundee DD1 5EH 2 Cancer Sciences Division, University of Southampton School of Medicine, Southampton General Hospital, Southampton SO16 6YD, UK To whom correspondence should be addressed Simon J. Powis, s.j.powis@dundee.ac.uk Received 7 February 2002; Revised 2 April 2002; Accepted 2 April 2002. |
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| Abstract |
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| The oxidoreductase ERp57 is an integral component of the peptide loading complex of major histocompatibility complex (MHC) class I molecules, formed during their chaperone-assisted assembly in the endoplasmic reticulum. Misfolded MHC class I molecules or those denied suitable peptides are retrotranslocated and degraded in the cytosol. The presence of ERp57 during class I assembly suggests it may be involved in the reduction of intrachain disulfides prior to retrotranslocation. We have studied the ability of ERp57 to reduce MHC class I molecules in vitro. Recombinant ERp57 specifically reduced partially folded MHC class I molecules, whereas it had little or no effect on folded and peptide-loaded MHC class I molecules. Reductase activity was associated with cysteines at positions 56 and 405 of ERp57, the N-terminal residues of the active CXXC motifs. Our data suggest that the reductase activity of ERp57 may be involved during the unfolding of MHC class I molecules, leading to targeting for degradation. |
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| Keywords: chaperone, endoplasmic reticulum, MHC class I, oxidoreductase ERp57, protein folding |
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